1. Field of the Invention
This invention relates in general to a new and improved digital voltmeter which incorporates an electro-optical indication of the waveform being measured.
2. Description of the Prior Art
Voltmeters which indicate the measured voltage in digital form by means of liquid crystal displays are known. The common designs contain a full-wave rectifier for measuring alternating voltages wherefore the indicated measured value corresponds only with the effective value of the alternating voltage when its waveform is sine-shaped. Designs are also known which measure and indicate the effective value of the voltage independently of its waveform. However, so far no voltmeter is known which supplies information regarding the waveform. Often the waveform of technical alternating voltages is distorted, and the periodic signal and control voltages in electronic systems and units are practically never sine-shaped. Thus, it is almost always more important to visually observe the waveform than to measure a form-dependent voltage value.
Oscilloscopes are known which make visible the variation in time of a periodic voltage through the use of a liquid crystal matrix. Because these oscilloscopes are used instead of the customary cathode ray oscillographs, they must have a liquid crystal matrix with very many image elements arranged in lines and columns. The technical difficulties connected with the production of liquid crystal matrices and the addressing devices required for this purpose increase with the number of cells an indicating matrix contains. Accordingly, the costs for indicating matrices having a larger number of cells are unproportionately high.